Pulse generator for ignition system



Feb. 15, 1966 w. Y. PETERS PULSE GENERATOR FOR IGNITION SYSTEM Filed Feb. 19, 1962 R3 m h 5 mm W wp/mw W M wk United States Patent 3,235,742 PULSE GENERATOR FOR IGNITION SYSTEM William Y. Peters, Tucson, Ariz., assignor to Jasper N. Cunningham, Los Angeles, Calif. Filed Feb. 19, 1962, Ser. No. 174,066 2 Claims. (Cl. 250233) This invention is directed to improvements in ignition systems and, more particularly, to an improved ignition system employing light sensitive apparatus for controlling the. selective generation of high voltage pulses at the cylinders of an internal combustion engine.

To provide high voltage pulses at the spark plugs of a multi-cylinder internal combustion engine in synchronism with the operation of the engine, ignition systems generally employ an electromechanical distributor which functions in synchronism with the engine to selectively apply a voltage across each of the spark plugs of the engine in a predetermined sequence. To accomplish this, distributors presently in commercial use generally utilize a multi-lobe cam positioned on a shaft which is coupled by a gearing arrangement to the crankshaft of the engine for rotation within the housing of the distributor in synchronism with the engine operation. Positioned within the housing and rotatably mounted on the distributor cam shaft is a breaker point mounting disc. A set of breaker points are secured to the disc which are positioned to mechanically open and close in response to physical contact with the lobes of the cam. The breaker points are connected to a voltage source and thus periodically complete an electrical circuit between the source and a distributor arm to apply voltage pulses to the distributor arm in synchronism with the engine operation. The arm is coupled to the upper end of the distributor cam shaft for rotation therewith. Displaced evenly around the distributor shaft is a plurality of electrical contacts, one associated with each spark plug of the engine. As the arm rotates with the distributor shaft it passes adjacent the electrical contacts in succession to thus effect a distribution of the voltage pulses to the spark plugs in a predetermined sequence in synchronism with the engine operation.

The breaker points, in combination with the lobes of the distributor cam shaft, therefore provide a timing for the voltage pulses applied to the distributor arm and hence to the spark plugs. Accordingly, the displacement of the breaker points relative to the distributor cam shaft as well as the adjustment of the points themselves is extremely critical. In practice, the breaker points are subject to continuous wearing by friction as well as corrosion and thus require frequent cleaning, adjustment and periodic replacement.

To combat these problems it has been suggested that photosensitive means be employed in conjunction with a member moving in synchronism with the motor operation as a substitute for the breaker point configuration of the conventional distributors. In the past, however, such photosensitive arrangements have been relatively bulky and expensive. Probably the greatest drawback to such prior arrangement, however, has been the complete lack of compatibility with presently existing distributor designs. In particular, to utilize such photosensitive arrangement has, in the past, required a complete redesign of the distributor configuration as well as a special mounting arrangement external to the distributor housing which presents a particular space problem in the present day compact auto engine compartment designs.

In contrast, the present invention provides an improved ignition system employing a photosensitive arrangement which is relatively inexpensive, being only slightly more expensive than the conventional ignition systems employing mechanical breaker points, and which is simple in de- "ice sign and completely compatible with the presently existing distributors.

To accomplish this the present invention, in a basic form includes a plate member for coupling to the breaker mounting disc in place of a set of breaker points and having a light source and a photosensitive element mounted thereon. The light source and photosensitive element are radially spaced from each other relative to the cam shaft. Coupled to the cam shaft for rotation therewith is a hollow timing drum. The drum is entirely situated within the housing of the distributor such that its outer surface passes between the light source and the photosensitive element. The surface of the drum passing between the light source and the photosensitive element has a plurality of openings, the number of openings corresponding to the number of cylinders in the engine. The openings are spaced from each other around the circumference of the drum to periodically allow light to pass from the light source to the photosensitive element. Coupled to the photosensitive element are circuit means for developing a high voltage signal in response to light received by the photosensitive element for selective application to the cylinders of the engine through the distributor arm.

Since electrical circuit elements having a fixed spacial relationship are employed in the present invention, the problems of frequent adjustment and cleaning associated with mechanical breaker points are nonexistent. Further, since the life of these circuit elements is extremely long, the ignition system of the present invention requires a minimum of servicing to periodically replace the light source. This effects a material reduction in the overall cost of the present ignition system relative to those employing mechanical breaker points.

By its particular mounting arrangement, the present invention is completely adaptable to any distributor design without necessitating the use of a special mounting arrangement external to the distributor. Also, by being mounted in place of a set of distributor points, the present invention is completely compatible with the present day methods of advancing and retarding the timing provided by the distributor, as by rotation of the breaker mounting disc within the housing with variations in the vacuum pressure in the intake manifold of the engine.

The above, as well as other features of the present invention, may be more clearly understood by reference to the following detailed description when considered with the drawings in which:

FIGURE 1 is a perspective representation of the photosensitive apparatus of the present invention mounted in a distributor;

FIGURE 2 is a schematic top view of the distributor represented in FIGURE 1; and

FIGURE 3 is a schematic representation of the electrical circuitry associated with a distributor employing the present invention.

As briefly described above, the photosensitive apparatus of the present invention is mounted within a distributor housing. A section of such a distributor is represented in perspective in FIGURE 1. As illustrated, the distributor includes a housing 10 which is mounted within the engine compartment of a multi-cylinder internal combustion engine (not shown). Extending longitudinally within the housing 10 is a distributor cam shaft 12. The distributor cam shaft 12 has a multi-lobed portion 14. By way of example, in an eight cylinder engine the lobed portion 14 is octagonal in shape to define eight lobes, one for each cylinder.

The distributor cam shaft 12 is coupled at one end by a gearing arrangement (not shown) to the crankshaft of the multi-cylinder internal combustion engine. An opposite end of the distributor shaft 12 is coupled to a distributor arm (not specifically shown). The cam shaft 12 a rotates in synchronism with the crankshaft and hence in synchronism with the operation of the engine. Accordingly, the distributor arm also rotates in synchronism with the operation of the engine.

Mounted within the housing is a breaker point mounting disc 16. The disc 16 is journaled on the cam shaft as represented generally at 18 to permit the disc to be moved angularly within the housing. The cam shaft 12 is free to rotate within the disc 16.

In conventional distributor designs a set of mechanical breaker points (not shown) are mounted on the disc 16 by a pair of screw members 20 and 22. The breaker points are positioned such that they close and open in response to physical contact with each lobe, such as 15, of the lobed portion 14 of the cam shaft 12. In this manner, the breaker points are closed and opened in synchronism with the operation of the engine. The closing and opening of the set of breaker points in response to the physical contact by each of the lobes in succession provide means for accurately timing the generation of high voltage pulses at each of the cylinders of the internal combustion engine as previously described.

In view of the critical timing provided by a combination of the breaker points and the lobes, the adjustment of the points as well as their position relative to the cam shaft 12 is highly critical. Due to the continuous rotation of the cam shaft 12, the set of breaker points are subject not only to corrosion but also to continuous wearing by friction. The breaker points of the conventional distributor thus require frequent adjustment and cleaning as Well as periodic replacement.

These disadvantages are overcome in the present invention by use of photosensitive apparatus in place of the conventional mechanical breaker points. To accomplish this, the present invention includes a plate member 24 which is mountable on the disc 16 by the screw members 20 and 22 in place of the set of breaker points. The plate 24 is arcuate in structure and includes an outwardly extending flanged portion 26. Mounted on the plate 24 is a light source 28. Radially displaced from the light source 28 and mounted on the flanged portion 26 is a photosensitive unit 30. Preferably, the photosensitive unit 30 is a photovoltaic detector, such as a solar cell. Thus, light striking the photosensitive unit 30 causes a voltage to be developed by the unit. These units are made extremely small and produce several tenths of a volt when illuminated by light. No voltage source is required for such a device.

To provide the timing for the distributor unit in accordance with the present invention, the light passing between the light source 28 and. the photosensitive unit 30 is modulated in synchronism with the engine operation by means coupled to the cam shaft 12. In a preferred embodiment, the light modulating means includes a hollow drum 32 which is coupled to the cam shaft 12 by means of an annula-r recess 34 which mates with the lobed portion 14 of the cam shaft 12. The drum 32 is constructed such that its outer surface passes between the light source 28 and the photosensitive unit 30. The outer surface of the drum 32 passing between the light source 28 and the photosensitive unit 30 includes a plurality of openings 36. The number of openings 36 corresponds to the number of cylinders in the engine. The openings 36 are evenly spaced from each other such that each opening is aligned with a different lobe of the lobed portion 14 as illustrated in FIGURE 2.

As the cam shaft 12 rotates in response to movement of the crankshaft of the engine, the drum 32 rotates there with to modulate the light passing to the photosensitive unit 30. Since the number of openings 36 correspond to the number of cylinders of the engine and since the openings 36 are evenly spaced around the periphery of the drum 32, movement of the drum 32 develops voltages at the photosensitive unit 30 in timed synchronism with the operation of the engine. The voltage developed at the photosensitive unit 30 may thus be utilized to provide high voltage pulses at each of the cylinders of the engine in a selective sequence synchronized with the engine operation.

Since the spacial relationship between the light source 28 and a photosensitive unit 30 is fixed and since no physical contact is made therebetween, adjustment of the photosensitive apparatus, after its initial installation, is unnecessary. Also, since the life of the light source and photosensitive unit is appreciably greater than that of a set of breaker points, replacement of the photosensitive apparatus is far less frequent than that of an ignition system employing mechanical breaker points. Thus, although the initial expense of the apparatus of the present invention may be greater than the conventional ignition systems, this initial cost is more than offset by the long life and trouble free operation of the unit compared with that of the breaker points.

By mounting the photosensitive apparatus on the plate 24, the present invention is completely compatible with the conventional distributor designs presently in use. For example, by simply unscrewing a set of breaker points, the plate 24 and the photosensitive apparatus may be substituted for the set of breaker points. Then, by sliding the drum 32 down over the lobed portion 14 of cam shaft 12, the means for modulating the light to the photosensitive apparatus is provided. Further, the photosensitive apparatus is mounted entirely within the housing of the distributor and neither increases the size of the distributor nor requires a special mounting arrangement external to the distributor to house the photosensitive unit or the light source.

The photosensitive apparatus of the present invention is also fully compatible with the operation of the conventional distributor. Thus, the conventional methods of advancing and retarding the timing of the distributor with changing motor conditions nee-d not be deviated from. For example, as illustrated in FIGURE 2, a diaphragm arrangement 38 may be provided that is coupled to the intake manifold of the engine by a tube 39. The diaphragm 38 is coupled through a suitable linkage arrangement 40 directly to the disc 16 in a conventional manner. In this way the timing of the distributor to advance or retard the spark developed at the cylinders of the engine is controlled by the vacuum pressure in the intake manifold. Thus, for example, if the engine is required to suddenly accelerate the pressure in the intake manifold drops causing a movement of the diaphragm and linkage arrangement to rotate the disc 16 in a counterclockwise direction relative to the housing 10. Rotation of the cam shaft 12 and the drum 32 then exposes the photosensitive unit 30 to light sooner than in its normal operation to provide an advance in the development of the high voltage pulses at the cylinders of the engine.

As previously described, a voltage signal developed at the photosensitive unit 30 is utilized by the ignition system of the present invention to develop a spark at each cylinder in timed succession and in synchronism with the engine operation. To accomplish this, a circuit arrangement, such as represented schematically in FIGURE 3, may be utilized.

Briefly, the circuit arrangement includes an electronic switching circuit 42 coupled between the photosensitive unit 30 and a conventional auto spark coil and condenser unit 44. The switching circuit 42 operates in combination with the photosensitive unit 30 to develop a high voltage pulse at the unit 44 for each voltage signal developed by the photosensitive unit 30. The unit 44 is, in turn, electrically connected to a distributor arm 46 which is coupled to rotate with the cam shaft 12. Spaced around the distributor arm is a plurality of electrical contacts 48, one electrically coupled to each spark plug 50 of the internal combustion engine. The electrical contacts 48 are spaced evenly around the distributor shaft 12 such that when a high voltage pulse is developed at the unit 44 the distributor arm 46 is in alignment with an electrical contact 48. In this manner an electrical circuit is completed to develop a spark at each of the cylinders in succession and in timed synchronism with the engine operation.

Considering specifically the circuit arrangement illustrated in FIGURE 3, to continuously maintain the light source 28 in an on condition, the source is coupled to a battery 52 through a switch 53. The photosensitive unit 30 for detecting the light from the light source 28 is coupled to the positive terminal of the battery 52 and through a biasing resistor 54 to the negative terminal of the battery 52. Coupled to a junction of the resistor 54 and the photosensitive unit 30 is a base element 56 of a PNP type transistor 58. The transistor 58 has its collector terminal 60 coupled to the negative terminal of the battery 52 and its emitter terminal 62 coupled through a biasing resistor 64 to the positive terminal of the battery 52. Coupled to the emitter 62 of the transistor 58 is a base terminal 66 of a PNP type transistor 68. The transistor 68 has its emitter terminal 70 coupled directly to the positive terminal of the battery 52 and its collector 72 is coupled to one terminal of the primary winding 74 of a step-up transformer 76 associated with the coil-condenser unit 44. The remaining terminal of the primary winding 74 is coupled directly to the negative terminal of the battery 52. Shunting the primary winding 74 is a condenser 78. The secondary winding 80 of the transformer 76 is coupled to ground and to the distributor arm 46 to complete the electrical switching circuit 42.

Through the biasing provided by the battery 52 and the associated biasing resistors, when light is being blocked from the photosensitive unit 30 the transistors 58 and 68 are biased to a conductive state. Accordingly, the condenser 78 is normally charged as indicated. When light strikes the photosensitive unit 30 a voltage is developed thereat which biases the base 56 of the transistor 58 positive relative to the emitter 62. This, in turn, causes the transistor 58 and hence the transistor 68 to suddenly switch to a non-conductive state. The condenser 78 then rapidly discharges through the primary winding 74 to produce a high voltage pulse across the secondary winding 80. During the discharge time of the condenser 74, a zener diode 82, which is coupled between the emitter 70 and collector 72 of the transistor 68, serves as a low impedance current path around the transistor 68, thereby protecting the transistor 68 when in a non-conductive state.

The high voltage pulse developed at the secondary winding 80 is then, in turn, applied to the distributor arm 46 for selective distribution to the spark plugs 50 in synchronism with the operation of the engine as previously described.

What is claimed is:

1. In a conventional distributor for a multi-cylinder internal combustion engine, the distributor having a hollow cylindrical housing, a cam shaft in the housing coupled for rotation in synchronism with the crankshaft of the engine, and a breaker point mounting disc journalled on the cam shaft Within the housing, the combination of:

a plate;

means for securing the plate to the breaker mounting disc in the housing in place of a set of breaker points;

a light source and a photosensitive element mounted on the plate, the light source and photosensitive element being disposed in the housing in radially spaced apart relation to one another and to the cam shaft;

a hollow timing drum coupled to the cam shaft for rotation therewith, the drum being situated entirely within the housing of the distributor such that the outer surface of the hollow drum passes between the light source and the photosensitive element, the surface of the drum passing between the light source and the photosensitive element having a plurality of openings therein spaced from each other around the periphery of the drum, whereby the light from the light source periodically passes to the photosensitive element;

and electrical circuit means coupled to the photosensitive element for developing a voltage signal in response to and in synchronism with light received by the photosensitive element for selective application to the cylinders of the engine.

2. The apparatus defined in claim 1 wherein the cam shaft of the distributor has a lobed portion extending within the housing and wherein the hollow timing drum is coupled to the cam shaft at the lobed portion by an annular recess which mates with the lobed portion of the cam shaft so that the timing drum is maintained in a predetermined angular relation relative to the cam shaft.

References Cited by the Examiner UNITED STATES PATENTS 2,084,267 6/1937 Hicks 123148 2,169,818 8/1939 Scott 123-148 3,020,897 2/1963 Sekine et al. 315-209 BENNETT G. MILLER, Primary Examiner. 

1. IN A CONVENTIONAL DISTRIBUTOR FOR A MULTI-CYLINDER INTERNAL COMBUSTION ENGINE, THE DISTRIBUTOR HAVING A HOLLOW CYLINDRICAL HOUSING, A CAM SHAFT IN THE HOUSING COUPLED FOR ROTATION IN SYNCHRONISM WITH THE CRANKSHAFT OF THE ENGINE, AND A BREAKER POINT MOUNTING DISC JOURNALLED ON THE CAM SHAFT WITHIN THE HOUSING, THE COMBINATION OF: A PLATE; MEANS FOR SECURING THE PLATE TO THE BREAKER MOUNTING DISC IN THE HOUSING IN PLACE OF A SET OF BREAKER POINTS; A LIGHT SOURCE AND A PHOTOSENSITIVE ELEMENT MOUNTED ON THE PLATE, THE LIGHT SOURCE AND PHOTOSENSITIVE ELEMENT BEING DISPOSED IN THE HOUSING IN RADIALLY SPACED APART RELATION TO ONE ANOTHER AND TO THE CAM SHAFT; A HOLLOW TIMING DRUM COUPLED TO THE CAM SHAFT; ROTATION THEREWITH, THE DRUM BEING SITUATED ENTIRELY WITHIN THE HOUSING OF THE DISTRIBUTOR SUCH THAT THE OUTER SURFACE OF THE HOLLOW DRUM PASSES BETWEEN THE LIGHT SOURCE AND THE PHOTOSENSITIVE ELEMENT, THE SURFACE OF THE DRUM PASSING BETWEEN THE LIGHT SOURCE AND THE PHOTOSENSITIVE ELEMENT HAVING A PLURALITY OF OPENINGS THEREIN SPACED FROM EACH OTHER AROUND THE PERIPHERY OF THE DRUM, WHEREBY THE LIGHT FROM THE LIGHT SOURCE PERIODICALLY PASSES TO THE PHOTOSENSITIVE ELEMENT; AND ELECTRICAL CIRCUIT MEANS COUPLED TO THE PHOTOSENSITIVE ELEMENT FOR DEVELOPING A VOLTAGE SIGNAL IN RESPONSE TO AND IN SYNCHRONISM WITH LIGHT RECEIVED BY THE PHOTOSENSITIVE ELEMENT FOR SELECTIVE APPLICATION TO THE CYLINDERS OF THE ENGINE. 